The present invention relates to a phthalocyanine crystal associating with an organic acceptor compound, its production method, and a high-sensitivity electrophotosensitive material containing the same.
With the development of a non-impact printer technique, an electrographic photoprinter using laser beam or LED as a light source,which is capable of attaining high image quality and high speed, has widely been used and a photosensitive material which responds to the demands has intensively been developed, recently. Among these photosensitive materials, an organic photosensitive material has widely been used because of its easy production, wide range of choice of photosensitive materials and high functional design freedom as compared with a conventional inorganic photosensitive material.
The organic photosensitive material includes, for example, single-layer type photosensitive material wherein an electric charge transferring material is dispersed in the same photosensitive layer, together with an electric charge transferring material, and function-separation type multi-layer type photosensitive material comprising an electric charge generating layer containing an electric charge generating material and an electric charge transferring layer containing an electric charge transferring material, which are mutually laminated.
When using a laser as a light source, a semiconductor laser is exclusively used because of its small size, cheap price, and simplicity. The oscillation wavelength of the semiconductor laser is not less than 750 nm at present and is limited to an infrared range. Accordingly, an organic photosensitive material having the sensitivity at a wavelength within a range from 750 to 850 nm is required.
As the electric charge generating material used in the organic photosensitive material, which satisfies the above demands, for example, polycyclic quinone pigment, pyrylium dye, squarium pigment, phthalocyanine pigment, and azo pigment have been suggested or put into practice.
Among the above electric charge generating materials, most popular phthalocyanine pigments include, for example, metal-free phthalocyanine having no center metal and metallic phthalocyanine having a center metal, and they have various crystal forms such as xcex1, xcex2, and xcex3 forms. The presence or absence and kind of the center metal as well as crystal form exert a large influence on the charging properties and sensitivity of the photosensitive material.
As the method of attaining a high-sensitivity photosensitive material using phthalocyanine, for example, a method of adding an organic acceptor compound in a photosensitive material has been studied. Japanese Unexamined Patent Publication (Kokai) No. 7-104495 describes a method of adding an organic acceptor compound in an electric charge generating layer of a multi-layer photosensitive material, while Japanese Unexamined Patent Publication (Kokai) No. 6-123984 describes a method of adding an organic acceptor compound in a binder of a single-layer photosensitive material.
However, any of the above methods is a method of adding an organic acceptor compound in the production process of a photosensitive material, that is, a method of adding an organic acceptor compound in the production process of a coating solution for photosensitive layer. A high-speed image forming apparatus has such a problem that the photosensitivity of its photosensitive material is poor, and a further improvement in photosensitivity is required.
Thus, an object of the present invention is to provide a novel phthalocyanine crystal useful as an electric charge generating material, and a production method thereof.
Another object of the present invention is to provide an extra-high-sensitivity electrophotosensitive material containing the above phthalocyanine crystal.
The present inventors have intensively studied to attain the above object and found that a photosensitive material containing, as an electric charge generating material, a phthalocyanine crystal produced by adding an organic acceptor compound in a photosensitive layer during the step of converting into a pigment, not produced by merely adding the organic acceptor in the photosensitive layer.
Thus, the present inventions relate to:
1. A phthalocyanine crystal in which an organic acceptor compound whose reduction potential to a reference electrode (Ag+/Ag) is not less than xe2x88x921.5 V and not more than xe2x88x920.5 V is associated with a phthalocyanine molecule.
2. The phthalocyanine crystal according to the above item 1, wherein said phthalocyanine is a metal-free phthalocyanine.
3. The phthalocyanine crystal according to the above item 1, wherein said phthalocyanine is a metal phthalocyanine represented by the general formula (1): 
xe2x80x83wherein M is a metal of the groups IIa, IIIa, IVa, Va, VII, Ib, IIb, IIIb, IVb or VIb on the periodic table, or a group containing the metal.
4. The phthalocyanine crystal according to the above item 3, wherein the group containing the metal is in the form of oxide, hydroxide, halide or cyanide.
5. The phthalocyanine crystal according to the above item 3, wherein M is TiO.
6. The phthalocyanine crystal according to the above item 1, wherein a solubility of said organic acceptor compound in a solvent in a coating solution for photosensitive layer is less than 10% by weight.
7. The phthalocyanine crystal according to the above item 6, wherein said solvent in a coating solution for photosensitive layer is alcohols, ketones or ethers.
8. The phthalocyanine crystal according to the above item 1, wherein said organic acceptor compound contains a compound represented by the general formula (2): 
xe2x80x83wherein R1, R2, R3 and R4 are the same or different and each represents a hydrogen atom, a halogen atom, or an alkyl, alkyl halide, alkoxy, aryl, aralkyl, cycloalkyl, cyano, nitro or amino group which may have a substituent, with a proviso that R1 and R2, or R3 and R4 may be combined with each other to form a ring.
9. The phthalocyanine crystal according to the above item 1, wherein said organic acceptor compound contains a compound represented by the general formula (3): 
xe2x80x83wherein R5, R6, R7, R8, R9, R10, R11 and R12 are the same or different and each represents a hydrogen atom, a halogen atom, or an alkyl, alkyl halide, alkoxy, aryl, aralkyl, cycloalkyl, cyano, nitro or amino group which may have a substituent, with a proviso that R5 and R6, R7 and R8, R9 and R10, or R11 and R12 may be combined with each other to form a ring; and A1 represents a saturated or unsaturated alkyl group which may have a substituent, an aryl group, or a heterocycle which may have a substituent.
10. The phthalocyanine crystal according to the above item 1, wherein said organic acceptor compound contains a compound represented by the general formula (4): 
xe2x80x83wherein X1, X2, X3 and X4 are the same or different and each represents an oxygen atom or C(CN)2; R13, R14 and R15 are the same or different and each represents a hydrogen atom, a halogen atom, or an alkyl, alkyl halide, alkoxy, aryl, aralkyl, cycloalkyl, cyano, nitro or amino group which may have a substituent; and Y1 and Y2 are the same or different and each represents a carbon atom, an oxygen atom, or a nitrogen atom.
11. The phthalocyanine crystal according to the above item 1, wherein said organic acceptor compound contains a compound represented by the general formula (5): 
xe2x80x83wherein X5 and X6 are the same or different and each represents an oxygen atom or C(CN)2; and R16, R17 and R18 are the same or different and each represents a hydrogen atom, a halogen atom, or an alkyl, alkyl halide, alkoxy, aryl, aralkyl, cycloalkyl, cyano, nitro or amino group which may have a substituent, with a proviso that R16 and R17 may be combined with each other to form a ring.
12. A phthalocyanine crystal in which an organic acceptor compound is associated with a phthalocyanine molecule, which is produced by adding the organic acceptor compound whose reduction potential to a reference electrode (Ag+/Ag) is not less than xe2x88x921.5 V and not more than xe2x88x920.5 V during a step of converting into a pigment.
13. A method of producing a phthalocyanine crystal in which an organic acceptor compound is associated with a phthalocyanine molecule, a step of which comprises: dissolving said phthalocianine together with said organic acceptor compound whose reduction potential to a reference electrode (Ag+/Ag) is not less than xe2x88x921.5 V and not more than xe2x88x920.5 V in a solvent capable of dissolving both of said phthalocyanine and said organic acceptor compound, adding the resulting solution to an aqueous methanol, thereby crystallizing said phthalocyanine associated with said organic acceptor compound.
14. An electrophotosensitive material comprising a conductive substrate and a photosensitive layer provided on the conductive substrate, wherein the photosensitive layer contains the phthalocyanine crystal of the above item 1 as an electric charge generating material.
15. An electrophotosensitive material comprising a conductive substrate and a photosensitive layer provided on the conductive substrate, wherein the photosensitive layer contains the phthalocyanine crystal of the above item 12 as an electric charge generating material.
16. The electrophotosensitive material according to the above item 14 or 15, which is a single-layer photosensitive material a layer of which comprises dispersing said phthalocyanine crystal and at least one of a hole transferring material and an electron transferring material into a binder resin.
17. The electrophotosensitive material according to the above item 16, wherein said single photosensitive layer contains both of the hole transferring material and the electron transferring material.
18. The electrophotosensitive material according to the above item 16, wherein said single photosensitive layer is formed by coating a coating solution which comprises adding said phthalocyanine crystal, at least one of the hole transferring material and the electron transferring material, and the binding resin to an organic solvent, and then drying the coated layer.
19. The electrophotosensitive material according to the above item 14 or 15, wherein said photosensitive layer is a laminated photosensitive layer which comprises laminating an electric charge generating layer containing said phthalocyanine crystal and an electric transferring layer containing at least one of a hole transferring material and an electron transferring material into a binder resin.
20. The electrophotosensitive material according to the above item 19, wherein said electric charge generating layer is formed by coating a coating solution which comprises adding said phthalocyanine crystal and the binding resin to an organic solvent, and then drying the coated layer.
21. The electrophotosensitive material according to the above item 16 or 19, wherein said binder resin contains a bis-Z type polycarbonate resin.
An electrophotosensitive material according to the present invention exhibits extra-high sensitivity. For example, it becomes possible to use the electrophotosensitive material even in high-speed image forming apparatuses because of its sufficient photosensitivity.